1. Field of the Invention
The present invention relates to a multi-display device and method thereof, in which a plurality of panels are connected to form a screen, and more particularly, to a multi-display device and method thereof that can minimize image cutting at a joint of a screen.
2. Description of the Related Art
In general, a multi-display device includes a plurality of display panels that are connected to form a large screen. In the beginning, a large screen TV, e.g., a large-sized TV for exhibitions was constructed by connecting a plurality of cathode-ray tubes (“CRTs”). In recent years, owing to the increased demand for large screens even in small-sized portable devices, for example, portable phones or personal digital assistants (“PDAs”), a device in which a large screen is formed by connecting flat panel displays (“FPDs”), such as liquid crystal displays (“LCDs”), field emission displays (“FEDs”), plasma display panels (“PDPs”), and organic light emitting diodes (“OLEDs”), has been introduced.
Conventionally, a multi-display device has been fabricated by connecting unit panels 10 in a row as illustrated in FIG. 1. In other words, a plurality of unit panels 10 are prepared and connected side by side to fabricate a multi-screen. However, in this case, the screen is not naturally connected at a joint between two display devices 12 of the panels 10 so that a viewer may have image cutting in the screen. Specifically, in an FPD shown in FIG. 1, a display device 12 forming pixels is mounted on a glass substrate 11 and a glass cover 13 is attached onto the glass substrate 11 to encapsulate the display device 12. In this case, since the glass cover 13 has a thickness “t” and the display device 12 is disposed inward from the glass cover 13, a distance between the two panels 10 (i.e., a cutting distance in the screen) becomes as much as “w”. It is difficult to reduce the distance “w” since the distance “w” is essential for the protection of the display device 12 using the glass cover 13. As a result, the FPD shown in FIG. 1 has a specific technical limit in improving the sense of image cutting at the joint of the screen.
In order to overcome this drawback, a new structure as illustrated in FIG. 2 in which two unit panels 21 and 22 are vertically stacked with a step difference has been proposed. Specifically, the first and second panels 21 and 22 are vertically disposed with a step difference therebetween, and an interface of a right pixel of the display device 21b of the first panel 21 and an interface of a left pixel of the display device 22b of the second panel 22 are fit on the same vertical line “L”, so that a feeling of image cutting at a joint of a screen made by the two panels 21 and 22 can be minimized. A cover 21c protecting the display device 21b of the first panel 21 overlaps and is partially disposed on a substrate 22a of the second panel 22. The display device 22b is protected by a cover 22c. In this structure, the two panels 21 and 22 form a connected screen, and a transparent plate 23 is installed on the substrate 22a of the second panel 22 so as to be coplanar with a substrate 21a of the first panel 21, so that the two panels 21 and 22 form a planar top surface.
In the foregoing conventional multi-display devices, two panels are hinge jointed to each other, thereby forming a folder type display that can be easily transported. Thus, the two panels are folded when the display device is transported, and unfolded to form one screen during use as illustrated in FIGS. 1 and 2.
However, since these multi-display devices are constructed such that two separated panels are unfolded to form a single screen, even if the panels are precisely fabricated according to the mechanical tolerances, air gaps still exist between the two panels. For example, as shown in FIG. 3, air gaps “G” exist not only between a bottom surface of the cover 21c of the panel 21 and a top surface of the substrate 22a of the panel 22 but also between a right surface of the cover 21c of the panel 21 and a left surface of the transparent plate 23. Thus, the conditions under which light is reflected are changed in the air gaps “G” so that the screen may look darker in areas corresponding to air gaps “G” than in other portions. In other words, when the screen has the air gap “G” with a different refractive index, light in the air gap “G” is refracted or reflected under different conditions, with the result that the air gap “G” looks dark to the eyes of a viewer. Therefore, even if the two panels 21 and 22 are disposed with a step difference in order to eliminate image cutting at the joint of the screen, another kind of image cutting is sensed in the screen due to a difference in luminance. Furthermore, the multi-display device shown in FIG. 1 amplifies the sense of image cutting in the screen because of the big distance “w” between the two display devices 12 of the panels 10.